Field of the Invention
The present invention relates to a transparent conductive film in which a transparent conductive layer is provided on a film substrate and a method for manufacturing the same. The transparent conductive film of the present invention is suitably used in touch panel applications.
Description of the Related Art
A transparent conductive film in which a transparent conductive thin film is formed on a transparent polymer substrate has been broadly used in transparent electrodes for solar cells, inorganic EL elements, and organic EL elements, electromagnetic wave shielding materials, touch panels, and the like. Especially, the installation rate of the touch panel in cellular phones, portable game machines, and the like has been increasing, and demand for a transparent conductive film has been rapidly increasing.
As a transparent conductive film used in a touch panel and the like, there has been broadly used a transparent conductive film in which a conductive metal oxide film of an indium tin complex oxide (ITO) or the like is formed on a flexible transparent polymer substrate such as a polyethylene terephthalate film. In such a transparent conductive film, from the viewpoint of preventing deterioration of visibility due to precipitation of a low molecular weight component such as an oligomer from the transparent polymer substrate, it has been proposed to form a cured resin layer (a hard coat layer) serving also as a diffusion preventing layer of the low molecular weight component on a substrate (Japanese Patent Application Laid-Open No. 2002-103504, for example).
Because the surface smoothness of the cured resin layer is generally high, the transparent conductive film in which the cured resin layer is provided on the surface of the substrate has such problems that it has inferior handling properties due to insufficient slipping property and anti-blocking properties. When a film is produced or processed, a long sheet is often wound in a roll to give a wound body in view of productivity and handling properties. However, the surface of the film having insufficient slipping property is easily scratched when the film is transported in a roll or when the film is wound up into a wound body, and its winding properties tend to deteriorate when the film is wound into a roll. When a film having inferior anti-blocking properties is wound into a roll, blocking easily occurs during the storage and the transportation of the wound body. From the viewpoint of solving these problems, a protective film (also referred to as a separator) is bonded onto the surface of the transparent conductive film, whereby the winding properties have been improved while protecting the surface of the transparent conductive film.
However, because the roll diameter and weight increase when the film is wound into a roll due to bonding of the protective film onto the surface of the film, it becomes difficult to improve workability due to the long film. In addition, an increase in cost and waste due to the use of the protective film may cause some problem. From the viewpoint of solving these problems, it has been proposed to improve the slipping property and the anti-blocking properties by forming irregularities on the surface of the cured resin layer by a method for incorporating fine particles into the cured resin layer (Japanese Patent Application Laid-Open No. 10-323931) or a method for using a coating composition containing two or more components that separate in phase from each other as a cured resin composition (Japanese Patent Application Laid-Open No. 2009-123685). From the viewpoint of balancing good slipping property, good anti-blocking properties, and good transparency at the same time, a method has been proposed in Japanese Patent Application Laid-Open No. 2010-157439 in which a coating composition containing two or more components that separate in phase from each other and a metal oxide or metal fluoride super fine particles having an average particle size of less than 200 nm are used together.
As described in Japanese Patent Application Laid-Open No. 10-323931, it is necessary to increase the particle size and the content of the particles in order to give sufficient easy slipping property by forming irregularities through addition of particles to the cured resin layer. Because of that, the transparency of the cured resin layer and the transparent conductive film tends to deteriorate due to light scattering of the fine particles, or the external appearance tends to be poor so that stripes caused by particles are generated during the formation of the cured resin layer.
On the other hand, it has been disclosed in Japanese Patent Application Laid-Open Nos. 2009-123685 and 2010-157439 to form a cured resin layer having a thickness of 3.5 μm from the coating composition containing two or more components that separate in phase from each other. With this configuration, a decrease of the transparency and generation of stripes are suppressed. However, it was found from the investigation by the present inventors that, as the thickness of the cured resin layer, in which the coating resin composition having two or more components that separate in phase from each other, increases, the handling properties of the film tend to deteriorate independent of the slipping property and the anti-blocking properties because the transparent conductive film curls due to heat generated when the transparent conductive layer is crystallized or when a touch panel is formed. On the other hand, when the thickness of the cured resin layer is decreased, the generation of curl is suppressed. However, it was found that it tends to be difficult to obtain stable anti-blocking properties and easy slipping property because the formation of irregularities of the surface is insufficient and because the formation of irregularities of the surface becomes uneven.